Partitioning Operators: Skip & SkipWhile
The partitioning operators split the sequence (collection) into two parts and return one of the parts.
Method | Description |
---|---|
Skip | Skips elements up to a specified position starting from the first element in a sequence. |
SkipWhile | Skips elements based on a condition until an element does not satisfy the condition. If the first element itself doesn't satisfy the condition, it then skips 0 elements and returns all the elements in the sequence. |
Take | Takes elements up to a specified position starting from the first element in a sequence. |
TakeWhile | Returns elements from the first element until an element does not satisfy the condition. If the first element itself doesn't satisfy the condition then returns an empty collection. |
Skip
The Skip()
method skips the specified number of element starting from first element and returns rest of the elements.
IList<string> strList = new List<string>(){ "One", "Two", "Three", "Four", "Five" };
var newList = strList.Skip(2);
foreach(var str in newList)
Console.WriteLine(str);
Four
Five
Skip Operator in Query Syntax
The Skip
& SkipWhile
operator is Not Supported in C# query syntax. However, you can use Skip/SkipWhile
method on a query variable or wrap whole query into brackets and then call Skip/SkipWhile
.
The following example demonstrates skip operator in query syntax - VB.NET
Dim skipResult = From s In studentList
Skip 3
Select s
SkipWhile
As the name suggests, the SkipWhile()
extension method in LINQ skip elements in the collection till the specified condition is true. It returns a new collection that includes all the remaining elements once the specified condition becomes false for any element.
The SkipWhile()
method has two overload methods. One method accepts the predicate of Func<TSource, bool>
type and other overload method accepts the predicate Func<TSource, int, bool>
type that pass the index of an element.
In the following example, SkipWhile()
method skips all elements till it finds a string whose length is equal or more than 4 characters.
IList<string> strList = new List<string>() {
"One",
"Two",
"Three",
"Four",
"Five",
"Six" };
var resultList = strList.SkipWhile(s => s.Length < 4);
foreach(string str in resultList)
Console.WriteLine(str);
Four
Five
Six
In the above example, SkipWhile()
skips first two elements because their length is less than 3 and finds third element whose length is equal or more than 4. Once it finds any element whose length is equal or more than 4 characters then it will not skip any other elements even if they are less than 4 characters.
Now, consider the following example where SkipWhile()
does not skip any elements because the specified condition is false for the first element.
IList<string> strList = new List<string>() {
"Three",
"One",
"Two",
"Four",
"Five",
"Six" };
var resultList = strList.SkipWhile(s => s.Length < 4);
foreach(string str in resultList)
Console.WriteLine(str);
One
Two
Four
Five
Six
The second overload of SkipWhile()
passes an index of each elements. Consider the following example.
IList<string> strList = new List<string>() {
"One",
"Two",
"Three",
"Four",
"Five",
"Six" };
var result = strList.SkipWhile((s, i) => s.Length > i);
foreach(string str in result)
Console.WriteLine(str);
Six
In the above example, the lambda expression includes element and index of an elements as a parameter. It skips all the elements till the length of a string element is greater than it's index.
SkipWhile operator in Query Syntax
The Skip
& SkipWhile
operator is NOT Supported in C# query syntax. However, you can use Skip/SkipWhile
method on a query variable or wrap whole query into brackets and then call Skip/SkipWhile
.
The following example demonstrates skip operator in query syntax - VB.NET
Dim skipResult = From s In studentList
Dim strList = New List(Of String) From {
"One",
"Two",
"Three",
"Four",
"Five",
"Six" }
Dim skipWhileResult = From s In studentList
Skip While s.Length < 4
Select s
Four
Five
Six